Withings integration - Sleep analyzer

Hi,

I’m basically trying to get a bed occupancy detector for automations and bought this sleep analyzer. I’m struggling to connect the Withings integration and am presented with this error after trying to allow the applet on their dev portal:

{“errors”:[{“message”:“redirect_uri_mismatch: The redirect URI provided is missing or does not match partner callback url”}]}

I used both these 2 urls for the applet and both give the same error sadly:
https://myname.duckdns.org/redirect/oauth
https://myname.duckdns.org/auth/external/callback

It has a native IFTTT compatiblity and even though I hate them, I tried to connect with webhooks, also gives this error: Your server returned a 404. Unable to make web request to myname.duckdns/api/mywebhookname

I’m running HA OS on a Linux VM.

I’m somewhat new to HA and not very good with yaml so please be gentle.

Thank you for any help.